EP2264277B1

EP2264277B1 - Overshot device

Info

Publication number: EP2264277B1
Application number: EP09007965A
Authority: EP
Inventors: Patrick Salvador
Original assignee: Atlas Copco Canada Inc
Current assignee: Atlas Copco Canada Inc
Priority date: 2009-06-18
Filing date: 2009-06-18
Publication date: 2012-08-01
Anticipated expiration: 2029-06-18
Also published as: US8955590B2; PE20121293A1; CL2011003167A1; MX2011013186A; CN102459805B; WO2010145984A2; ES2391696T3; PL2264277T3; WO2010145984A3; AU2010261956B2; RU2529040C2; PT2264277E; US20120125612A1; CN102459805A; CA2763137C; RU2012101638A; CA2763137A1; AU2010261956A1; ZA201108791B; EP2264277A1

Description

TECHNICAL FIELD

The present invention relates to a device comprising an overshot for handling the core barrel after each drilling cycle, for example.

BACKGROUND ART

During diamond drilling for geotechnical application or mining exploration, an inner-tube is filled up with rock core. When the inner-tube is full, the operator needs to recover it. The inner-tube is linked with a head assembly or back end that permits to recover the inner-tube. An overshot is used like a fishing system to grab the head assembly. The overshot is in turn linked with a steel wire comprised in a wire line hoist system.
When an overshot and an inner tube are pulled out of a rod string for core recovery, there is a possibility that the overshot releases the spear head assembly by accident. If this happens, there is risk for workers injury and damage to the equipment.
The document US 6,997,493 teaches a lockable overshot comprising an elongated body, lifting dogs and a locking sleeve. The ends of the lifting dogs are configured for latching a conventional spearhead point there between.
A locking sleeve is rotatable on the body between a locked state preventing ends of the lifting dogs from pivoting away from other to release a previously latched spearhead point, and an unlocked state where the locking sleeve allows the lifting dogs to move so that the ends can be pivoted away from each other to release a previously latched spearhead point.
When the overshot goes out of the rod string, the operators have to stop, to lock, retrieve, unlock manually by rotating the locking sleeve into the unlocked position and manually pivot the two lifting dogs to separate the overshot from the spearhead assembly and get the core sample out. This is time consuming. Further, there is possibility operators choose not to lock the overshot at all. The operation can be difficult if dirt is present in the mechanism. At that time there is a risk for accident. The overshot also has the possibility to accidentally release the spearhead while still in the drill string, dropping the inner tube assembly to the bottom of the hole, causing damage to equipment.
The document US 4,004,835 teaches an overshot comprising a tubular sleeve and a scissor like mechanism arranged moving as a unit. A spring bearing on the top end of the scissors tends to force them down into closing movement against an inner taper of the bottom ring of the tubular sleeve. The solution permits downward movement which releases the fishing neck. This avoids placing undue strain on the overshot.
Thus, there are needs to increase the safety and efficiency when working with an overshot. These needs cannot be fulfilled by overshot according to the above-mentioned prior art.

SUMMARY OF THE INVENTION

An object of the invention is to increase the safety when working with overshot. The problem to be solved is to increase the control of the release operation of a caught spearhead.
According to a first aspect of the present invention, the invention provides an overshot comprising a first part with an elongated body adapted to be connected to a hoisting line in one end and with a tubular opening arranged/designed to receive a spearhead in the other end. The overshot further comprises a second part with a scissor like mechanism comprising two lifting dogs arranged to pivot around a common pivot pin and arranged connected with a biasing means. The elongated body comprises a central, axially extending slot and the scissor like mechanism is arranged with the common pivot pin sliding in the slot between a first end position where the biasing means is arranged to close the lifting dogs and thereby lock a spearhead received in the tubular opening and a second end position where opening means comprising an opening pin is arranged to force the lifting dogs open to release a spearhead received in the tubular opening.
The solution according to the invention provides an overshot where the risk of accidental release of a head assembly is eliminated.
The solution may also be adapted with pump-in seals to be used in an underground application.
Further, the solution according to the invention provides a safe and secure way of operating an overshot. The solution lends the operator full control of locking and releasing an overshot.
The lifting portions of the lifting dogs are designed with a curve to wrap around the neck of a spearhead, decreasing the likelihood of an accidental release. They also have curvature on the outside surface to interact with the matching curved features within the overshot head to reduce wear and improve the distance required to lock the lifting dogs within the overshot head.
The feature up/upwards is defined as a direction axially along the overshot towards the hoisting line connection i.e. up in Figure 2-4. The feature down/downwards is defined as a direction axially along the overshot towards the head assembly i.e. same as force of gravity and down in Figure 2-4.
The biasing means is defined arranged to pivot the lifting dogs to a closed position, where the lifting dogs are in a gripping position due to its extension force.
The opening means is defined arranged to force the lifting dogs to pivot to an open position, where the lifting dogs are separated in a non-gripping position due to a manual force overcoming the extension force of the biasing means.
The force exerted by the biasing means will be translated onto the pivot pin causing the lifting dogs to move downwards to the bottom position, away from the hoist line end of the overshot so that the lifting portion of the lifting dogs are locked within the inside features of the overshot head. At the same time, the force of gravity acting on the scissor like mechanism combines to the movement.
According to a feature of the invention, the biasing means comprises an extension spring arranged connecting the lever portions of the lifting dogs.
According to a feature of the invention, the opening means comprises an opening pin arranged stationary in the elongated body. The opening pin is arranged between the lifting dogs and protruding from the elongated body surface. According to one alternative, the stationary opening pin is positioned axially above the slot, between the slot and the hoisting line connection end.
According to another alternative, the stationary opening pin is positioned axially below the slot, between the slot and the tubular opening end.
According to a feature of the invention, the opening pin is a sliding pin arranged sliding in the slot and connected to the pivot pin by a sliding bar.
According to a feature of the invention, the sliding pin is arranged in parallel with the pivot pin.
According to a second aspect of the present invention, the invention provides a method of operating an overshot comprising a first part with an elongated body connected to a hoisting line in one end and with a tubular opening arranged/designed to receive a spearhead in the other end. The overshot further comprises a second part with a scissor like mechanism comprising two lifting dogs and a common pivot pin, where the lifting dogs are connected via a biasing means. The elongated body comprises a central, axially extending slot and the scissor like mechanism is arranged with the common pivot pin sliding in the slot. The method comprising manually operating the common pivot pin to slide in the slot from a first end position, where the biasing means is arranged to pivot the lifting dogs to grip a spearhead received in the tubular opening to a second end position, and forcing the lifting dogs to pivot into a non-gripping position due to the sliding movement such that the spearhead is released when the pivot pin reaches the second position.
Manually holding the lifting dogs against the opening means in the up/top position will force the lifting dogs open and thus allowing the release of the spearhead. To release the inner-tube from the overshot at the surface, the operator has to push the spear head inside the overshot and maintain the sliding bar in the up/top position. Alternatively, the tension of the lifting dogs is released on the spearhead to start with and then the operator has to push the sliding bar and maintain up a pin and continue the movement/pushing of the sliding bar to up/top position. This is safe, easy and quickly done and improves the productivity.
The overshot according to the invention is a mechanism for latching onto a spearhead that greatly reduces the chances of accidental release of the spearhead. The forced pivoting of the lifting dogs into a non-gripping position is a secure and controllable operation of a spearhead. This in turn guarantees the secure operation of the overshot and assures the workers safety.
According to a third aspect of the invention, the invention provides an use of an overshot as described above in an underground application in conjunction with an underground adapter adapted with a propulsion seal to propel the overshot through the drill string (not shown) using fluid under pressure.
The invention is considered to comprise alternative features with at least one secondary pin placed in the overshot head to prevent the lifting dogs from rotating out of the side openings of the overshot head. This pin can be located either above or below the main pivot pin.
This pin can also be used to slide against the lifting dogs to force them closed when moved to the bottom position or open when moved to the top position.
The secondary pin can also be joined to the main pivot pin by an external sliding bar, so that it moves in conjunction with the main pivot and to stop the lifting dogs from pivoting out of the side openings of the overshot head.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be explained more closely by the description of different embodiments thereof and with reference to the appended drawing in which:

Figure 1 is an exploded view of an overshot arrangement according to the invention,
Figure 2 is an overshot arrangement according to the invention in a closed position,
Figure 3 is a cross section of the overshot arrangement in Figure 2,
Figure 4 is a cross section of the overshot arrangement in Figure 2,
Figure 5 is a cross section of an overshot arrangement according to the invention in a closed position gripping a head assembly,
Figure 6a is a schematic view of an overshot arrangement according to the invention in a position of releasing a head assembly,
Figure 6b is a cross section of an overshot arrangement according to the invention in a position of releasing a head assembly,
Figure 7 is a cross section of an overshot arrangement with an underground adapter and propulsion seal according to the invention,
Figure 8 is an overshot arrangement according to the invention with a pump-in seal,
Figure 9 is an alternative overshot arrangement according to the invention.

DESCRIPTION OF ALTERNATNE EMBODIMENTS

Figure 1 is an exploded view of an arrangement according to the invention comprising an overshot 1 to be used like a fishing system to grab a head assembly. This will be described in detail below.
The overshot 1 ( Figure 2 ) comprises a first part with an elongated body 2 adapted to be connected to a hoisting line in one end 2a and with an axial tubular opening in the other end 2b arranged to receive a spearhead 4 (Figure 7). The overshot 1 further comprises a second part with a scissor like mechanism 5 comprising two lifting dogs 6, 7 each comprising a circular opening 22. A pivot pin 8 is arranged through the openings 22 such that the lifting dogs are arranged to pivot around the common pivot pin 8 ( Figure 3 ). Each lifting dog 6, 7 comprise a lever portion 6a, 7a and a lifting portion 6b, 7b. The lever portions 6a, 7a are connected with a biasing means 10 in the form of an extension spring 10a attached between connection points 10a, 10b.
The elongated body 2 comprises a central, axially extending slot 12 and the scissor like mechanism 5 is arranged with the common pivot pin 8 sliding in the slot 12 ( Figure 4 ). The scissor like mechanism 5 is arranged to move during operation such that the common pivot pin 8 is sliding in the slot 12 between a first end position 13 and a second end position 14 (Figure 2).
An area 21 around the slot 12 in the overshot body 2 (Figure 1) for the pivot pin 8 is machined to allow retaining bar or washer to slide with the pivot pin. This area is also machined big enough to allow clearance for the operator to easily hold the pivot pin and a control lever 18 in the top, open position to allow the release of the spearhead 4.
The pivot pin 8 slides within the elongated body 2. In the first end position 13 ( Figure 5 ), the common pivot pin 8 is in its lowermost position in the slot 12. The scissor like mechanism 5 is locked gripping a spear head 4 received in the tubular opening 3 due to the extension spring 10a forcing the lever portions 6a, 7a to close. In this first end position 13, the lifting portions 6b, 7b are mechanically contained within the body 2, prevented from opening and releasing the spearhead 4. Manually holding the scissor like mechanism 5 against the opening means 9 in the up/top position will force the lifting dogs 6, 7 open and thus allowing the release of the spearhead 4. To release the inner-tube from the overshot at the surface, the operator has to push the spear head inside the overshot and maintain the sliding bar in the up/top position. Alternatively, the tension of the lifting dogs is released on the spearhead to start with and then the operator has to push the sliding bar and maintain up a pin and continue the movement/pushing of the sliding bar 18 to up/top position.
.This is safe, easy and quickly done and improves the
Figure 6a is a cross section of an overshot arrangement according to the invention in a position between first 13 and second end positions 14 on the way of releasing the head assembly.
In the second position 14 ( Figure 6b ), the common pivot pin 8 is in its uppermost position in the slot 12. The elongated body 2 is arranged to comprise an opening means 9 arranged to force the two lever portions 6a, 7a away from each other in the second position 14. The opening means 9 is a pin 9a arranged stationary attached to the elongated body 2. The pin 9a is arranged in parallel with the common pivoting pin 8 (Figure 4).
The elongated body 1 further comprises a pair of elongated adjacent and parallel side openings 16, 17 arranged such that the lifting portions 6b, 7b can pass/exit the inside walls during pivoting of the lifting dogs 6, 7 to an open position.
Each lifting dog 6, 7 comprise a sliding surface curvature 26a, 26b which is arranged to follow/slide along the stationary opening pin 9a during the pivoting/pushing ( Figure 6a , 6b ) to an open position. Thus, the scissor like mechanism 5 is open due to the forced pivoting of the lever portions 6a, 7a apart into the second position 14. Consequently, a spear head 4 received in the coaxial tubular opening 3 of the overshot is released when the pivot pin 8 is in the second position 14.
When the force is removed from the control lever 18, the force of the spring 10a will pull the lifting dog lever portions 6a, 7a together and close the scissor like mechanism 5, which will move downwards partly due to the sliding surface curvatures 26a, 26b leaving the sliding contact with the pivot pin 8 and partly due to forces of gravity.
In each of the overshot arrangements in Figure 1-4, at least one control lever 18 comprising a circular opening 23 and a flat surface 20 is connected to/arranged on the pivot pin 8 for the manual operation of the overshot. The flat surface 20 is adapted to be the surface to touch during pushing.
The pin used as a pivot point for the lifting dogs are secured to the assembly using cotter pins and/or retaining rings at both end to facilitate ease of assemble and reduction of tools and parts.
The slot has been designed into the overshot head to allow the pivot pin to move approximately 3/8" - ½". This movement allows the lifting dogs to move in and out of the locked position and interact with the slide pin as mentioned above.
Figure 7 is an arrangement with an overshot 1. The overshot 1 is connected to an underground adapter 27 comprising a propulsion seal 28 and support washer 29.
Figure 8 is an overshot 1 according to the invention adapted with pump-in seals 30 to be used in an underground application.
Figure 9 is an overshot 2 wherein the opening means 9 is a sliding opening pin 9b arranged sliding in the slot 12 and connected to the pivot pin by a sliding bar 19.
The method of operating an overshot will be explained in the following. The overshot 1, arranged hanging in a hoisting line (not shown), is lowered down in a drilled hole like a fishing system to grab a spearhead assembly connected to an inner tube. In this position, the scissor like mechanism 5 is closed due to the spring's action 10a. When the overshot 2 reaches the spearhead 4, the spearhead is free to pass into the coaxial tubular opening 3 of the overshot. The overshot is designed such that the weight of the elongated body 2a, i.e. the gravity forces keeps the elongated body hanging down while the spearhead 4 pushes the scissor like mechanism 5 in the opposite direction, up in e.g. Figure 3. The forced pushing upwards makes the opening means i.e. the stationary pin 9a forcing the lifting dogs 6, 7 to pivot into an open position where the spearhead 4 is passing in between the lifting portions 6b, 7b. In this position the forced pushing upwards is ended, the scissor like mechanism is sliding/falling back downwards. During this sliding/falling back, the lifting dogs are automatically pivoting back into the closed position and the head 4 is automatically locked. The lifting portions 6b, 7b of the lifting dogs are designed with a curve wrap 24 (Figure 1) around the neck to wrap around the neck of the spearhead, increasing the gripping of the spearhead. The lifting dogs also have curvature 25 (Figure 1) on the outside surface to interact with the matching curved features 15 within the overshot (Figure 3) to reduce wear and improve the distance required to lock the lifting dogs 6, 7 within the overshot head 1.
When the overshot and the back end or head assembly are connected for the core recovery, the overshot is gripping and the head 4 is in this way/moment locked.
When it is time to release the inner-tube at the surface from the overshot, the operator has to push the spear head 4 inside the overshot 1 and maintain up the pivot pin 8 with the control lever 18 to up/top position. Alternatively, the tension of the lifting dogs is released on the spearhead to start with and then the operator has to maintain up the pivot pin 8 and push the control lever 18 to up/top position.
During the pushing movement, the scissor like mechanism 5 is pushed upwards with the pivot pin 8 sliding in the slot 12. The design of the overshot 1 is based on the requirement that the mentioned manual pushing upwards of the pivot pin 8 makes the lifting dogs 6, 7 pivoting. This is achieved due to the scissor like design with a common pivot pin 8 and of each lever portions 6a, 7a of the lifting dogs comprising a curvature surface 26a, 26b adapted to slide along the stationary pin 9a during the operators pushing of the control lever 18. When the manual pushing upwards overcomes the extension force of the extension spring 10a, the pushing and the design of the curvature surfaces 26a, 26b in combination with the stationary pin 9a forces the lever positions 6a, 7a to pivot apart. Consequently, the scissor like mechanism 5 is forced open and the spear head 4 is released.

Claims

A device with an overshot device (1) comprising a first part with an elongated body (2) adapted to be connected to a hoisting line in one end and with a tubular opening (3) arranged/designed to receive a spearhead (4) in the other end, the overshot (1) further comprising a second part with a scissor like mechanism (5) comprising two lifting dogs (6, 7) arranged to pivot around a common pivot pin (8), characterized in that the lifting dogs (6, 7) are connected via a biasing means (10), the elongated body (2) comprises an central, axially extending slot (12), and the scissor like mechanism (5) is arranged with the common pivot pin (8) sliding in the slot (12) between a first end position (13) where the biasing means (10) is arranged to close the lifting dogs (6, 7) such that a spearhead (4) received in the tubular opening is locked and a second end position (14) where an opening means (9) comprising an opening pin is arranged to force the lifting dogs (6, 7) open against the force of the biasing means (10) such that a spearhead (4) received in the tubular opening (3) is released.
A device according to claim 1, wherein the opening pin is a stationary opening pin (9a) attached to the elongated body (2).
A device according to claim 2, wherein the stationary opening pin (9a) is positioned axially above the slot (12), between the slot and the hoisting line connection end.
A device according to claim 2, wherein the stationary opening pin (9a) is positioned axially below the slot (12), between the slot and the tubular opening end.
A device according to claim 3 or 4, wherein the stationary opening pin (9a) is arranged in parallel with the pivot pin (8).
A device according to claim 1, wherein the opening pin is a sliding opening pin (9b) arranged sliding in the slot (12) and connected to the pivot pin by a sliding bar (19).
A device according to claim 6, wherein the sliding opening pin (9b) is arranged in parallel with the pivot pin (8).
A device according to any preceding claim, wherein the body (2) comprises locking means (15) arranged to lock the lifting dogs (6, 7) inside the elongated body.
A method of operating a overshot device (1) comprising a first part with an elongated body (2) connected to a hoisting line in one end and with a tubular opening (3) arranged/designed to receive a spearhead (4) in the other end, the overshot (1) further comprising a second part with a scissor like mechanism (5) comprising two lifting dogs (6, 7) and a common pivot pin (8), where the lifting dogs (6, 7) are connected via a biasing means (10), the elongated body (2) comprises an central, axially extending slot (12), and the scissor like mechanism (5) is arranged with the common pivot pin (8) sliding in the slot (12), the method comprising manually operating the common pivot pin (8) to slide in the slot (12) from a first end position (13), where the biasing means (10) is arranged to pivot the lifting dogs (6, 7) to grip a spearhead (4) received in the tubular opening (3) to a second end position (14) where an opening means is arranged to force the lifting dogs (6, 7) to pivot into a non-gripping position due to the sliding movement such that the spearhead (4) is released when the pivot pin (8) reaches the second position (14).
A method according to claim 9, wherein locking means (15) are locking the lifting portions (6b, 7b;) of the lifting dogs within the interior of the elongated body (2).
Use of a device according to any of claims 1-7 in an underground application in conjunction with an underground adapter (27) adapted with a propulsion seal (28) to propel the overshot (1) through the drill string using fluid under pressure.